The present invention is directed to an alloy which finds particular use in a nuclear reactor and is characterized by its improved swelling resistance and phase stability in both the annealed as well as the cold work condition in comparison with an AISI type 316 stainless steel.
With the advent of the nuclear age and the materials problems associated therewith, it was believed that the AISI type 316 stainless steel because of its austenitic character and which is strengthened through a solid solution strengthening addition would prove to be ideally suited for use in a nuclear reactor. This conclusion was buttressed by the fact that the AISI type 316 stainless steel appeared to possess the desired strength characteristics at elevated temperatures. It was soon found however that even after low fluid reactor irradiation copious amounts of radiation induced precipitation were evident in the microstructure and the material was subjected to relatively high swelling. It therefore became apparent that it was necessary to alter the chemical composition AISI type 316 stainless steel in an attempt to eliminate the phase instabilities and to provide improved swelling resistance without seriously adversely affecting the strength characteristics of the fundamental alloy. To this end the alloy of the present invention appears to fulfill these primary requisites.